A. Field of the Invention
The present invention relates generally to the hot pressing of layers of natural or reconstituted wood products as in the manufacture of pressed wood panels for furniture making, and, more particularly, to a printed vulcanized fibre-based product and process for making the same.
B. Description of the Related Art
Vulcanized cellulose fibre is well-suited as a cross band and face veneer material for wood paneling. Vulcanized fibre has extremely high tensile strength in all directions so that a thin vulcanized fibre can be used to securely anchor wooden sheets or veneers in place. Moreover, its cellulosic nature is highly compatible with wood so that splitting and checking of the face veneers are eliminated.
Vulcanized fibre can vary in thickness from about 0.25 millimeters to about 0.80 millimeters, and preferably are colored with pigments to match the colors of face veneers. Also these vulcanized fibres can be laminated from about two to about six very thin plies of cellular paper. The pigments are conveniently added to the beater stock from which rolls of paper are made, and no more than about 0.5% to about 2% pigment need be used, based on the dry weight of the fibre.
The papers used for making vulcanized fibre are formed continuously into rolls on Fourdrinier paper machines from 100% Kraft or sulfite pulp. Each roll preferably contains about 2.5 to about four ounces of fibre per square yard, based on the dry weight of the fibre.
The paper rolls are dried to a moisture content of about 2% to about 4%, then superimposed and fed in superimposed condition through the vulcanizing tank and then through the purification tanks, followed by drying. The vulcanizing treatment causes the superimposed plies to adhere to each other, and after the drying they will not delaminate. The purification tanks wash the vulcanizing chemical from the sheets. The laminate may then be calendared to a uniform thickness and smooth surface.
The vulcanized fibre web can be wound onto a roll or sheeted. At that stage, the web may be dry, that is have a moisture content of about 6% to 7%.
FIG. 1 is an isometric view of a conventional fancy face five-ply natural wood veneer-based panel 100. Panel 100 consists of a particleboard core 22 assembled with a cross band sheet 104 on each surface, and with wood veneer face sheets 106, 108 over each cross band sheet 104. Cross band sheets 104 may or may not be made from vulcanized fibre. One of the face sheets, for example, may be a decorative wood veneer sheet 106, as shown in FIG. 1, which contains a decorative wood grain pattern. The other face sheet 108 may also be decorative or merely a plain sheet of wood veneer.
The assembled items are then pressed between plates heated to about 275° F. and a pressure of about 150 pounds per square inch. The heat penetrates into the assembly to cure adhesive layers on the cross band sheets 104 after a few minutes, when the face sheets 106, 108 are no thicker than about 30 millimeters.
After sufficient time has elapsed, the press is opened and the cured panel 100 is removed. The edge faces of the cured panel 100 may then be edge-banded by cementing to them decorative or other face strips. Strips of a cross band sheet may be used for this purpose with the help of standard adhesives such as ethylene-vinyl acetate and polyamide hot melt adhesives used for edge banding. Cold-setting adhesives such as the usual urea-formaldehyde and polyvinyl acetate adhesives may also be used for this purpose as well as for cross banding if desired.
The core 102 of FIG. 1 is shown as a single piece as large as the panel, but it may be assembled from two or more pieces preferably cemented together as needed to make up the desired length and width. A particularly desirable arrangement has a particleboard core surrounded on its four edges with one or one-half inch wide strips of solid wood, and this is cross banded without requiring edge banding.
While the conventional fancy face five-ply natural wood veneer-based panel products offer many advantages over natural wood products, the five-ply products require significant manufacturing steps and do not offer the visual appearance of a natural wood product. Furthermore, conventional fancy face five-ply natural wood veneer-based panel products cannot be processed (i.e., stained, sanded, lacquered, etc.) like a natural wood product.
Thus, there is a need in the art for a cellulose-based product that overcomes the problems of the related art.